The invention relates to machines for making hot beverages, such as coffee, tea or chocolate. More particularly, the invention relates to improvements in coffee-, tea- or analogous brewing machines of the type wherein the housing resembles or constitutes a carafe with a chamber for the liquid (such as water or milk) to be heated and with a chamber for freshly brewed beverage.
German Utility Model No. 71 34 272 discloses a coffee making machine wherein the housing resembles a carafe and wherein an electric heater serves to heat a body of water. Heated water flows upwardly through a riser and contacts a supply of comminuted coffee beans. The thus obtained beverage gathers in a chamber having a dispensing spout to facilitate pouring of the beverage into cups or other receptacles. The electric heater is a so-called immersion heater which dips into the body of water in the respective chamber of the housing. The beverage-receiving chamber is disposed beneath a coffee filter. A cup-shaped container for boiling water is removably inserted into the top portion of the housing and receives hot water from the water-containing chamber by way of the overflow type outlet of the aforementioned riser. A fluidtight seal is provided between the container and the upper end of the water-receiving chamber. The container comprises a partition which divides its interior into two compartments and enables hot liquid to overflow from one compartment into the other. A water-discharging outlet of the container is located at a level above the filter to furnish a stream of hot water which penetrates through the supply of comminuted coffee beans on the filter and into the beverage-receiving chamber below. The outlet of the container communicates with both compartments and is designed in such a way that the rate of outflow of hot water from one of the compartments can exceed the rate of outflow from the other compartment. A plug-type cover or bung is used to close the upper end of the housing above the container.
The just described machine is operated as follows: The filter receives a supply of communicated coffee beans, and the container is placed on top of the water-receiving chamber prior to insertion of the cover. The immersion-type heating element is set in operation to heat the body of water in the respective chamber. When the temperature of heated water reaches a predetermined value, the pressure of developing vapors forces hot water to flow upwardly through the riser and into the container wherein one of the compartments is filled ahead of the other. The outlet of the container discharges hot water onto the supply of comminuted coffee beans on the filter, and the thus obtained beverage flows into the respective chamber.
The capacity of the container must be selected in such a way that the container is capable of confining the entire body of water in the housing with the exception of that quantity which is in the process of being discharged from the container. In other words, the capacity of the container must match or approximate that of the chamber for fresh water.
The above described conventional machine exhibits several important advantages. Thus, the housing is compact and the freshly brewed beverage can be dispensed without the need for a separate coffee pot as is customary in many presently known automatic coffee or tea makers. However, the machine also exhibits certain serious drawbacks, particularly as concerns the quantity of hot coffee which can be brewed therein. The quantity is limited, primarily because the pressure in the region of the supply of comminuted coffee beans and the pressure of hot water which is supplied to the filter cannot exceed atmospheric pressure. The rate of flow of freshly brewed beverage from the filter is slow, especially if the filter contains a relatively large quantity of comminuted coffee beans. This is the reason that such machines failed to gain widespread acceptance. As a rule, machines of the aforedescribed type are used soley for the brewing of small quantities of fresh coffee.
It is also known to design a coffee or tea making machine in such a way that the interior of the housing can be maintained at an elevated pressure. This renders it possible to brew larger quantities of hot beverages per unit of time. Thus, and since the pressure of hot water which is caused to flow toward the filter in order to contact the comminuted beans is well above atmospheric pressure, the water can penetrate through the filter at a relatively high rate. However, such types of brewing machines are invariably furnished with separte pots or like vessels for collection and temporary storage of freshly brewed beverages. Moreover, the housings of conventional machines wherein hot water can be maintained at an elevated pressure do not resemble or constitute carafes with adjacent but separate chambers for fresh liquid and hot beverage.